A disc drive has become one of the essential data-accessing devices in a personal computer nowadays. As a disc drive is hit by a foreign object, the deformation of the structure of the disc drive might result in damage to the inner elements of the disc drive. An example would be the collision between the damper and the turntable of the disc drive, causing the damper to be deformed. Since any damage to the inner elements of the disc drive is likely to cause malfunction, the disc drive needs to avoid collision.
FIG. 1 illustrates the chassis structure of a conventional disc drive which includes a main chassis 102 and a sub chassis 104. The main chassis 102 is the primary frame of the disc drive, and generally, the sub chassis 104 is connected to a turntable and an optical pickup head (not shown in FIG. 1). The main chassis 102 and the sub chassis 104 are attached together with a cam rack 106. The cam rack 106 has a shaft 108, and a slot 1062 engaged with a stick (not shown in FIG. 1) disposed on the sub chassis 104 so that the sub chassis 104 is able to change its position when the cam rack 106 is moved.
When the cam rack 106 is in a first position as shown in FIG. 1, the sub chassis 104 stays in a low position. When the cam rack 106 is in a second position as shown in FIG. 2, the sub chassis 104 shifts to a high position correspondingly. FIG. 3 illustrates the backside view of the tray of a conventional disc drive. Referring to FIG. 3, the backside of the tray 202 includes a track 204 which has a first end 206 and a second end 208. As the tray 202 enters the disc drive in the direction of the arrow shown in FIG. 1, the shaft 108 engages with the track 204 and then moves from the first end 206 toward the second end 208 along the track 204. The cam rack 106 is gradually shifting toward the left of FIG. 1 when the shaft 108 approaches the second end 208. Eventually, the cam rack 106 is located at the second position as the tray 202 has completely entered the disc drive.
FIG. 4 is the explosive view of the inner components of a conventional disc drive. The cam rack, the tray, and the optical pickup head are not illustrated in FIG. 4 so as to clearly indicate the structures of the main chassis 102 and the sub chassis 104. The turntable 112 is disposed on a motor 114, which is disposed on the sub chassis 104. The sub chassis 104 has a stick 1042 configured to engage with the slot 1062 of the cam rack 106 shown in FIG. 1. The damper 110 is disposed on an assembly base 116, which is disposed within the housing of the disc drive (not shown). As mentioned above, when the tray 202 enters the disc drive, the sub chassis 104 will move from the low position to the high position and thus lead the turntable 112 and the optical pickup head (not shown) to ascend. Thereafter, the turntable 112 and the damper 110 together are able to clip a disc disposed on the tray 202 tightly by magnetic attraction between the turntable 112 and the damper 110.
Generally speaking, the shaft 108 will not move farther when reaching the second end 208 of the track 204 as shown in FIG. 5. However, the shaft 108 might depart from the track 204 in the direction of the arrow shown in FIG. 5 when the disk drive is hit by a foreign object or during a proceeding of a bumping test. If the shock on the disc drive is too huge, even the track 204 cannot retain the shaft 108, and the shaft 108 departs from the track 204 over the wall thereof Once the shaft 108 departs from the track 204, the tray 202 cannot freely move in and out of the disc drive.
Moreover, when the cam rack 106 is in the second position and the sub chassis 104 is in the high position, the turntable 112 and the damper 110 will be very close to each other. Once a collision resulting from a shock occurs, it is very likely that either the turntable 112 or the damper 110 gets so deformed that either cannot operate normally.